California Code, Vehicle Code - VEH § 21116

(a) No person shall drive any motor vehicle upon a roadway located on a levee, canal bank, natural watercourse bank, or pipeline right-of-way if the responsibility for maintenance of the levee, canal bank, natural watercourse bank, or pipeline right-of-way is vested in the state or in a reclamation, levee, drainage, water or irrigation district, or other local agency, unless such person has received permission to drive upon such roadway from the agency responsible for such maintenance, or unless such roadway has been dedicated as a public right-of-way.

(b) For this section to be applicable to a particular levee, canal bank, natural watercourse bank, or pipeline right-of-way, the state or other agency having responsibility for maintenance of the levee, canal bank, natural watercourse bank, or pipeline right-of-way shall erect or place appropriate signs giving notice that permission is required to be obtained to drive a motor vehicle thereon and giving notice of any special conditions or regulations that are imposed pursuant to this section and shall prepare and keep available at the principal office of the state agency or other agency affected or of the board of such agency, for examination by all interested persons, a written statement, in conformity with the existing rights of such agency to control access to the roadway, describing the nature of the vehicles, if any, to which such permission might be granted and the conditions, regulations, and procedure for the acquisition of such permission adopted pursuant to this section.

(c) Nothing in this section prohibits the establishment of bicycle paths or routes (as prescribed by Article 6.5 (commencing with Section 5078) of Chapter 1 of Division 5 of the Public Resources Code) on levees, canal banks, natural watercourse banks, or pipeline rights-of-way.